Draw frames are mainly used to produce a fiber web that is as uniform as possible from a multiple number of fiber slivers. For this purpose, the draw frame has one or more drafting units, which in turn comprise a series of drafting elements, typically in the form of several successively arranged pairs of rollers, whereas the fiber slivers are guided between the respective pairs of rollers by clamping. Since the pairs of rollers feature peripheral speeds that vary and increase in the running direction of the sliver, the fiber slivers are finally drafted and thereby made uniform.
With known draw frames, it is generally the case that a sliver guide is placed in the entrance area, i.e. in the area in which the fiber slivers run into the drafting unit; this comprises, for example, a multiple number of vertically extending rods, between which the individual fiber slivers are guided.
If the individual fiber slivers feature different qualities (such as different thicknesses or fiber lengths), the fiber web leaving the draw frame also usually features a quality fluctuating over its width, since the mixing of the fiber slivers is only limited within the draw frame.